High melt strength polypropylene and method for preparing same

Abstract

High melt strength polypropylene and a method for preparing the high melt strength polypropylene are provided. [Solution] A high melt strength resin composition comprising: a) unfunctionalized polypropylene; b) at least one acrylate salt, such as zinc diacrylate, calcium diacrylate, or aluminum triacrylate, in a total amount of 0.1% to 5% by weight, based on the weight of the unfunctionalized polypropylene; and c) at least one acid neutralizer in a total amount of 0.005% to 5% by weight, based on the total weight of the at least one acrylate salt. The high melt strength polypropylene is obtained by compounding the resin composition at a processing temperature between 185°C and 260°C.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 000,174, entitled "High Melt Strength Polypropylene and Method Therefor," filed March 26, 2020, the entire contents of which are incorporated herein by reference for all purposes.

[0002] FIELD OF THE INVENTION The present invention relates generally to high melt strength polypropylene and methods for preparing high melt strength polypropylene. [Background technology]

[0003] Polypropylene is a widely used plastic that has favorable properties in the solid state, such as high modulus, high tensile strength, and good heat resistance. However, due to its linear molecular structure, polypropylene generally has a relatively low melt strength, which adversely affects its processability. The low melt strength limits many applications of polypropylene resin, such as foam molding, sheet extrusion thermoforming, extrusion blow molding, and extrusion coating.

[0004] An alternative approach to the production of high melt strength polypropylene is described in US Pat. Nos. 5,623,999 and 5,723,999.

[0005] One way to improve the melt strength of polypropylene is to add long chain branches to the polymer structure. However, the long chain branches incorporated within the polymer structure can make the polymer too rigid, impairing the thermoplastic properties of the polymer. Therefore, developing a method to produce high melt strength polypropylene (HMS-PP) without compromising other desirable properties is of great interest. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] US Patent Application Publication No. 2012 / 0220730 [Patent Document 2] US Patent Application Publication No. 2015 / 0031838 Summary of the Invention

[0007] Generally, polypropylene has a low melt viscosity, which limits (narrows) its processing window during molding operations such as foam extrusion, sheet extrusion, thermoforming, blow molding, extrusion coating, and film formation, and also reduces the properties of articles molded by such processes. The present invention overcomes these limitations by reactively blending an acrylate, such as zinc diacrylate, with polypropylene in the presence of an acid neutralizer, such as zinc oxide.

[0008] It has been unexpectedly discovered that when a resin composition containing an acrylate salt such as zinc diacrylate and polypropylene is melt extruded, controlling the compounding (processing) temperature to be between 185°C and 260°C or between 220°C and 240°C maximizes the melt strength of the resulting compounded polypropylene.

[0009] Furthermore, it has been surprisingly discovered that the presence of an acid neutralizer (e.g., zinc oxide) when compounding polypropylene with an acrylate effectively reduces the content of unreacted acrylic acid in the extruded polypropylene and improves the melt strength of the compounded polypropylene (compared to the melt strength of a similar polypropylene / acrylate composition compounded without the acid neutralizer under the same processing conditions). The melt strength is the strength measured by conditioning the prepared sample at 170°C for 5 minutes, followed by heating at 170°C at a strain rate of 0.1 s as described in the Examples. -1 The elongational viscosity was measured at 100°C.

[0010] One embodiment of the present invention provides a resin composition useful for preparing high melt strength polypropylene, comprising: a) unfunctionalized polypropylene; b) at least one acrylate salt selected from the group consisting of zinc diacrylate, calcium diacrylate, and aluminum triacrylate, in a total amount of 0.1 wt % to 5 wt %, based on the weight of the unfunctionalized polypropylene; and c) at least one acid neutralizer in a total amount of 0.005 wt % to 5 wt %, based on the total weight of the at least one acrylate salt.

[0011] Another embodiment of the present invention provides a method for producing high melt strength polypropylene, comprising compounding a resin composition comprising: a) unfunctionalized polypropylene; b) at least one acrylate salt selected from the group consisting of zinc diacrylate, calcium diacrylate, and aluminum triacrylate, in a total amount of 0.1 wt% to 5 wt%, based on the weight of the unfunctionalized polypropylene; and c) at least one acid neutralizer, in a total amount of 0.005 wt% to 5 wt%, based on the total weight of the at least one acrylate salt, at a processing temperature between 185°C and 260°C.

[0012] In yet another embodiment, the present invention provides a high melt strength polypropylene obtainable by compounding, at a processing temperature between 185°C and 260°C, a resin composition comprising: a) unfunctionalized polypropylene; b) at least one acrylate salt selected from the group consisting of zinc diacrylate, calcium diacrylate, and aluminum triacrylate, in an amount of 0.1 wt% to 5 wt%, based on the weight of the unfunctionalized polypropylene; and c) at least one acid neutralizer in a total amount of 0.005 wt% to 5 wt%, based on the total weight of the at least one acrylate salt. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a graph showing the effect of processing temperature on extensional viscosity. Detailed Description of the Invention

[0014] The resin composition according to the present invention comprises at least the following components: a) non-functionalized polypropylene; b) at least one acrylate salt selected from the group consisting of zinc diacrylate, calcium diacrylate, and aluminum triacrylate, in a total amount of 0.1 to 5% by weight, based on the weight of the non-functionalized polypropylene; and c) at least one acid neutralizer, in a total amount of 0.005 to 5% by weight, based on the total weight of the at least one acrylate salt.

[0015] (non-functionalized polypropylene) The polypropylene used in the resin composition of the present invention is non-functionalized polypropylene, i.e., polypropylene that does not carry or contain functional groups such as carboxylic acid or anhydride functional groups. However, as a result of chemical and / or grafting reactions that may occur during the formulation of the resin composition, the resulting high melt strength polypropylene may contain a polymer backbone that is partially substituted with functional groups such as acrylic acid groups and / or acrylate salt groups. These polypropylenes may be prepared using polymerization methods known in the art. For example, suitable polypropylenes can be prepared using Ziegler-Natta catalysts, metallocene catalysts, or free radical initiation.

[0016] Suitable non-functionalized polypropylenes include polypropylene homopolymer and polypropylene Suitable comonomers include both olefinic comonomers (propylene copolymers in which propylene monomer is copolymerized with one or more comonomers, excluding any functionalized comonomers) and copolymers of propylene (propylene copolymers in which propylene monomer is copolymerized with one or more comonomers, excluding any functionalized comonomers). Suitable comonomers include, for example, olefinic comonomers such as ethylene, propylene, butene, pentene, hexene, heptene, octene, nonene, decene, and the like, and generally include α-olefins.

[0017] According to certain embodiments, the total amount of such comonomers in the polypropylene copolymer is limited relative to the amount of propylene, for example, the polypropylene copolymer may contain one or more non-functionalized comonomers in a total amount of 20% by weight or less, 15% by weight or less, 5% by weight or less, 2% by weight or less, or 1% by weight or less, with the remainder being propylene.

[0018] However, in another embodiment of the present invention, the non-functionalized polypropylene is an alloy of polypropylene and at least one other polymer. For example, the at least one other polymer can be present in the alloy in an amount of up to 50 wt%, up to 40 wt%, up to 30 wt%, up to 20 wt%, up to 10 wt%, or up to 5 wt%, based on the total weight of the alloy (the remainder being polypropylene homopolymer and / or polypropylene copolymer). Blends or alloys of polypropylene homopolymer and polypropylene copolymer are also possible.

[0019] Suitable polypropylenes include propylene random copolymers, propylene impact copolymers, syndiotactic polypropylene, isotactic polypropylene, and atactic (amorphous) polypropylene.

[0020] The non-functionalized polypropylene has, for example, a molecular weight distribution (M w / M n ) may be 1.0 to about 50, about 1.5 to about 15, or about 2 to about 12.

[0021] The unfunctionalized polypropylene has a melting point (T m ) (measured by DSC) may be, for example, at least about 100°C, from about 115°C to about 175°C, or from about 128°C to about 173°C.

[0022] The unfunctionalized polypropylene may, for example, contain about 15% by weight or less, about 12% by weight or less, about 10% by weight or less, about 6% by weight or less, about 5% by weight or less, or about 4% by weight or less xylene solubles (XS) (as measured by ASTM D5492-06).

[0023] Unfunctionalized polypropylene has a density (measured by ASTM D1505-18) of, for example, about 0.880 g / cm 3 ~Approx. 0.925g / cm 3 may be.

[0024] The non-functionalized polypropylene may have, for example, a melt flow index (MFI) of 0.2 g / 10 min to 2000 g / 10 min, or 1 g / 10 min to 50 g / 10 min (2.16 kg, 230° C.).

[0025] Mixtures or blends of two or more different non-functionalized polypropylenes may be employed in the resin composition.

[0026] According to some embodiments of the present invention, the resin composition contains no or limited amounts of any type of polymer other than non-functionalized polypropylene. For example, the resin composition may contain 10% by weight or less, 5% by weight or less, 1% by weight or less, or 0% by weight of any type of polymer other than non-functionalized polypropylene, based on the total weight of the resin composition.

[0027] (acrylates) Acrylate salts useful in the present invention may be selected from zinc diacrylate, calcium diacrylate, aluminum triacrylate, and combinations or mixtures thereof, with zinc diacrylate being generally preferred.

[0028] Such acrylates are present in the resin composition used to produce high melt strength polypropylene in a total amount of 0.1% to 5% by weight, based on the weight of the unfunctionalized polypropylene. According to one embodiment, the resin composition contains one or more such acrylates (e.g., zinc diacrylate) in an amount of 0.5% to 3% by weight, based on the weight of the unfunctionalized polypropylene. The acrylates may also be added to the resin composition as a masterbatch.

[0029] (acid neutralizer) In the context of the present invention, the term "acid neutralizing agent" includes any substance capable of neutralizing carboxylic acids, particularly acrylic acid. That is, the acid neutralizing agent at least partially deprotonates the carboxylic acid, particularly under the temperatures and conditions encountered during formulation of the resin composition. As a result of such neutralization, the carboxylic acid may be at least partially converted to the corresponding salt. For example, zinc oxide may react with acrylic acid to form zinc diacrylate (water being produced as a by-product of such reaction).

[0030] Types of acid neutralizing agents include, but are not limited to, metal oxides, metal hydroxides, alkali metal hydroxides, alkali metal carbonates, alkaline earth metal oxides, alkaline earth metal carbonates, alkali metal bicarbonates, metal carboxylates, alkali metal carboxylates, alkaline earth metal carboxylates, and combinations thereof. Compounds containing polyvalent metals (e.g., zinc, titanium) or alkaline earth metals (e.g., calcium, barium, magnesium) are suitable acid neutralizing agents. Specific examples of suitable acid neutralizing agents include zinc oxide, zinc hydroxide, calcium oxide, barium oxide, magnesium oxide, titanium dioxide, sodium carbonate, sodium bicarbonate, calcium carbonate, magnesium carbonate, sodium hydroxide, potassium hydroxide, zinc salts of fatty acids (e.g., zinc stearate), calcium salts of fatty acids (e.g., calcium stearate), and combinations thereof. Alternatively, the at least one acid neutralizing agent comprises zinc oxide.

[0031] Typically, the resin composition of the present invention includes one or more acid neutralizing agents in a total amount of 0.005% to 5% by weight, based on the total weight of the at least one acrylate. For example, the resin composition may include one or more acid neutralizing agents, such as zinc oxide (ZnO), in a total amount of 1% to 3% by weight, based on the total weight of the at least one acrylate. The acid neutralizing agent may be added to the resin composition separately, incorporated as the non-neutralized portion of the acrylate component, or added as a masterbatch.

[0032] Either or both of the acrylate salt and the acid neutralizer may be provided in the form of a masterbatch. A suitable carrier resin for the masterbatch is a polyolefin resin, which may be selected from polypropylene, polyethylene, mixtures thereof, and copolymers thereof. The masterbatch may then be combined with a polypropylene resin to prepare a high-strength polypropylene resin composition. The masterbatch is prepared by blending the acrylate salt and / or the acid neutralizer with the carrier resin at a temperature of 190°C or less. The masterbatch may contain 40% to 70% by weight of the acrylate salt. When the masterbatch contains both the acrylate salt and the acid neutralizer, the masterbatch may contain 0.005% to 5% by weight of the acid neutralizer, based on the total weight of the at least one acrylate salt. For example, a masterbatch containing both the acid neutralizer and the acrylate salt may be prepared. The batch may contain one or more acid neutralizers, such as zinc oxide (ZnO), in a total amount of 1 to 3 wt % based on the total weight of the at least one acrylate salt. When the masterbatch contains only an acid neutralizer, the masterbatch may contain 1 to 25 wt % of the acid neutralizer.

[0033] As used herein, the term "masterbatch" refers to a resin composition in which an additive is present at a concentration of 5% to 90% by weight, alternatively 20% to 80% by weight, alternatively 40% to 70% by weight. In this disclosure, a polyolefin carrier may contain either or both of an acrylate salt and an acid neutralizer and be used as a masterbatch for these additives. Masterbatches are used to precisely distribute additives into bulky resins.

[0034] (Other additives) One or more additional additives other than acrylates and acid neutralizers can be included in the resin composition containing at least one polypropylene, including antioxidants, fillers other than acid neutralizers, colorants other than acid neutralizers, flame retardants other than acid neutralizers, blowing agents other than acid neutralizers, clarifiers, scratch prevention additives, dust prevention additives, nucleating agents, and stabilizers, and combinations thereof. When such additives are present in the resin composition, they are typically present in an amount of 5 wt% or less, based on the weight of the resin composition.

[0035] Enhanced melt strength of non-functionalized polypropylene is achieved by dispersing an acrylate (zinc diacrylate, calcium diacrylate, and / or aluminum triacrylate) in the polymer melt in the presence of an acid neutralizer, reacting and grafting the acrylate portion of the acrylate with the non-functionalized polypropylene in the polymer melt, followed by associating zinc, calcium, and / or aluminum ions in a post-melt extrusion conversion step to produce sheets, foams, films, and molded or shaped parts. The resin composition comprising, consisting essentially of, or consisting of polypropylene, acrylate, and acid neutralizer may be compounded using any suitable equipment capable of intimately blending the resin composition at effective processing temperatures, such as a single- or twin-screw extruder, a Banbury mixer, or a roll mill, as described in more detail below.

[0036] Reactive mixing, such as reactive extrusion, can be used to combine the components of the resin composition to form high melt strength polypropylene. Formation of high melt strength polypropylene typically involves a single reactive extrusion, although the composition from the initial extrusion can be subjected to one or more additional extrusions. This process can be carried out using any type of extruder, including twin-screw extruders. The extruder can be a pellet extruder or one that produces sheet or any other known type of extrudate.

[0037] The compounding is carried out at a processing temperature above the melting point of polypropylene, particularly between 185°C and 260°C (inclusive). It has been discovered that operating within this processing temperature range, particularly between 220°C and 240°C or between 225°C and 235°C (inclusive), can increase the melt strength of the polypropylene. In particular, compounding the resin composition at a processing temperature of about 230°C has been found to maximize the melt strength of the resulting polypropylene. In other words, compounding at a processing temperature above about 230°C results in a decrease in melt strength.

[0038] However, the high melt strength polypropylenes of the present invention may have a wide variety of mechanical and other properties, as there may be many embodiments within the scope of the present invention. In fact, the high melt strength polypropylenes produced from the resin compositions according to the present invention have enhanced melt strengths as compared to the unfunctionalized polypropylene employed as a component of the starting resin composition, as evidenced, for example, by increased torque, dynamic rheology, and extensional viscosity. For example, the melt strength of these high melt strength polypropylenes is 0.1 s at 170°C. -1 The elongational viscosity measured at a strain rate of 0.1 s at 170°C for the non-functionalized polypropylene used as one component of the resin composition, which is the starting material. -1The increase in extensional viscosity of the enhanced melt strength polypropylene may be at least 25%, at least 50%, at least 100%, at least 150%, at least 200%, at least 300%, at least 400%, at least 500%, at least 600%, at least 700%, at least 800%, at least 900%, at least 1000%, or at least 1500% greater than the extensional viscosity measured at a strain rate of 1000%. The increase in extensional viscosity of the enhanced melt strength polypropylene may range from 25% to 2000%, 25% to 1500%, 50% to 1500%, 100% to 1250%, 200% to 1250%, 300% to 1000%, 100% to 900%, or 150% to 1000%. Furthermore, when an acid neutralizer is included in the resin composition that is processed to form the high melt strength polypropylene, the high melt strength polypropylene has a reduced free acrylic acid content compared to a comparable polypropylene compound processed under the same conditions in the absence of the acid neutralizer. The inclusion of an acid neutralizer in the resin composition has the further desirable effect of increasing the melt strength.

[0039] The high melt strength polypropylene of the present invention can be used alone or as a masterbatch in combination with other polymer resins such as polypropylene homopolymers, impact copolymers, etc.

[0040] The high melt strength polypropylene produced according to the present invention is suitable for use in a number of applications, including all known applications for linear polypropylene, for example, foaming, sheet extrusion thermoforming, extrusion blow molding, extrusion coating, fibers, films, and the like.

[0041] In one embodiment, the invention is a method for producing high melt strength polypropylene, the method comprising reactively mixing a combination of unfunctionalized polypropylene; an acrylate salt selected from the group consisting of zinc diacrylate, calcium diacrylate, and aluminum triacrylate; and an acid neutralizing agent; and recovering a polypropylene product having increased melt strength (relative to the starting unfunctionalized polypropylene).

[0042] In one embodiment, articles can be obtained by subjecting the high melt strength polypropylene of the present invention to plastic molding processes such as foam extrusion, sheet extrusion, film extrusion, thermoforming (including sheet extrusion thermoforming), blow molding (including extrusion blow molding, injection blow molding, and injection stretch blow molding), extrusion coating, etc. The high melt strength polypropylene can be molded into end-use articles such as, for example, packaging, office supplies, structural support materials, laminate compositions, polymeric foam substrates, decorative surfaces, outdoor furniture, storefront signs and displays, household and consumer goods, building insulation, cosmetic packaging, outdoor replacement materials, lids and food / beverage containers, consumer electronics, cookware, electronic components, automotive parts, enclosures, medical supplies, toys, plumbing, etc.

[0043] Exemplary, non-limiting aspects of the present invention can be summarized as follows. Aspect 1: A resin composition for use with high melt strength polypropylene, comprising, consisting essentially of, or consisting of: a) unfunctionalized polypropylene; b) at least one of zinc diacrylate, calcium diacrylate, and aluminum triacrylate, in a total amount of 0.1% to 5% by weight, based on the weight of the unfunctionalized polypropylene; and c) at least one acid neutralizing agent in a total amount of 0.005% to 5% by weight, based on the total weight of the at least one acrylate salt. Aspect 2: The resin composition of Aspect 1, wherein the acid neutralizing agent comprises at least one of a metal oxide, a metal hydroxide, an alkali metal hydroxide, an alkali metal carbonate, an alkaline earth metal oxide, an alkaline earth metal carbonate, an alkali metal bicarbonate, a metal carboxylate, an alkali metal carboxylate, an alkaline earth metal carboxylate, or a combination thereof. Aspect 3: The resin composition of Aspect 1 or 2, wherein the acid neutralizing agent comprises at least one of zinc oxide, zinc hydroxide, calcium oxide, barium oxide, magnesium oxide, titanium dioxide, sodium carbonate, sodium bicarbonate, calcium carbonate, magnesium carbonate, sodium hydroxide, potassium hydroxide, a zinc salt of a fatty acid, a calcium salt of a fatty acid, or a combination thereof. Aspect 4: The resin composition of any one of Aspects 1 to 3, wherein the at least one acid neutralizing agent comprises zinc oxide. Aspect 5: The resin composition of any one of Aspects 1 to 4, further comprising zinc diacrylate. Aspect 6: The resin composition of any one of Aspects 1 to 5, wherein the resin composition does not contain an organic peroxide. Aspect 7: The resin composition of any of Aspects 1 to 6, wherein the unfunctionalized polypropylene has a melt flow index (MFI) of 0.2 g / 10 min to 2000 g / 10 min (2.16 Kg, 230° C.). Embodiment 8: The resin composition of any of Embodiments 1-7, wherein the unfunctionalized polypropylene is at least one of a polypropylene homopolymer, a polypropylene copolymer, or an alloy of polypropylene and at least one additional polymer. Aspect 9: The resin composition of any of Aspects 1-8, wherein the unfunctionalized polypropylene is prepared using at least one Ziegler-Natta catalyst. Embodiment 10: The resin composition of any of Embodiments 1-8, wherein the unfunctionalized polypropylene is prepared using at least one metallocene catalyst. Aspect 11: The resin composition of any of Aspects 1-8, wherein the unfunctionalized polypropylene is prepared using a free radical initiation reaction. Aspect 12: The resin composition of any one of Aspects 1 to 11, containing 0.5% by weight to 3% by weight in total of at least one of zinc diacrylate, calcium diacrylate, and aluminum triacrylate. Aspect 13: The resin composition of any one of Aspects 1 to 12, further comprising one or more additives selected from the group consisting of antioxidants, fillers other than acid neutralizers, colorants other than acid neutralizers, flame retardants other than acid neutralizers, blowing agents other than acid neutralizers, clarifying agents, scratch prevention additives, dust prevention additives, nucleating agents, and stabilizers. Aspect 14: A method for producing high melt strength polypropylene, the method comprising the steps of compounding at a processing temperature between 185°C and 260°C a resin composition comprising, consisting essentially of, or consisting of: a) unfunctionalized polypropylene; b) at least one of zinc diacrylate, calcium diacrylate, or aluminum triacrylate in a total amount of 0.1% to 5% by weight based on the weight of the unfunctionalized polypropylene; and c) at least one acid neutralizing agent in a total amount of 0.005% to 5% by weight based on the total weight of the at least one acrylate salt. Embodiment 15: The method of embodiment 14, wherein the processing temperature is between 220°C and 240°C. Embodiment 16: The method of embodiment 14 or 15, wherein the processing temperature is about 230°C. Embodiment 17: The method of any of embodiments 14-16, wherein the compounding is carried out using a single or twin screw extruder, a Banbury mixer, or a roll mill. Aspect 18: The method of any of Aspects 14-17, wherein the resin composition is melt extruded. Embodiment 19: The method of any of embodiments 14-18, wherein the combining results in acrylate moieties from at least one of zinc diacrylate, calcium diacrylate, or aluminum triacrylate being grafted to the unfunctionalized polypropylene. Aspect 20: The acid neutralizing agent is selected from the group consisting of a metal oxide, a metal hydroxide, an alkali metal hydroxide, an alkali metal carbonate, an alkaline earth metal oxide, an alkaline earth metal carbonate, an alkali metal bicarbonate, and the like. 20. The method of any of embodiments 14-19, comprising at least one of a metal carboxylate, a metal carboxylate, an alkali metal carboxylate, an alkaline earth metal carboxylate, or a combination thereof. Aspect 21: The method of any of Aspects 14-20, wherein the acid neutralizing agent comprises at least one of zinc oxide, zinc hydroxide, calcium oxide, barium oxide, magnesium oxide, titanium dioxide, sodium carbonate, sodium bicarbonate, calcium carbonate, magnesium carbonate, sodium hydroxide, potassium hydroxide, a zinc salt of a fatty acid, a calcium salt of a fatty acid, or a combination thereof. Embodiment 22: The method of any of embodiments 14-21, wherein the at least one acid neutralizing agent comprises zinc oxide. Embodiment 23: The method of any of embodiments 14-22, comprising zinc diacrylate. Aspect 24: The method of any one of Aspects 14 to 23, wherein the resin composition does not contain an organic peroxide.

[0041] Aspect 25: The method of any of Aspects 14-24, wherein the unfunctionalized polypropylene has a melt flow index (MFI) from 0.2 g / 10 min to 2000 g / 10 min (2.16 Kg, 230°C). Embodiment 26: The method of any of embodiments 14-25, wherein the unfunctionalized polypropylene is at least one of a polypropylene homopolymer, a polypropylene copolymer, or an alloy of polypropylene and at least one additional polymer. Aspect 27: The method of any of Aspects 14 to 26, wherein the resin composition contains at least one of zinc diacrylate, calcium diacrylate, or aluminum triacrylate in a total amount of 0.5% to 3% by weight, based on the weight of the unfunctionalized polypropylene. Aspect 28: The method of any one of Aspects 14 to 27, wherein the resin composition further comprises at least one of an antioxidant, a filler other than an acid neutralizer, a colorant other than an acid neutralizer, a flame retardant other than an acid neutralizer, a blowing agent other than an acid neutralizer, a clarifying agent, a scratch prevention additive, a dust prevention additive, a nucleating agent, and a stabilizer. Aspect 29: The method of any of Aspects 14-26, wherein at least one of the acrylate salt and the acid neutralizing agent is in the form of a masterbatch that includes a polyolefin as a carrier resin for the masterbatch. Aspect 30: A high melt strength polypropylene obtainable by compounding at a processing temperature between 185°C and 260°C a resin composition comprising, consisting essentially of, or consisting of: a) unfunctionalized polypropylene; b) at least one of zinc diacrylate, calcium diacrylate, or aluminum triacrylate, in a total amount of 0.1% to 5% by weight, based on the weight of the unfunctionalized polypropylene; and c) at least one acid neutralizer, in a total amount of 0.005% to 5% by weight, based on the total weight of the at least one acrylate salt.

[0041] Aspect 31: The high melt strength polypropylene of Aspect 30, wherein the processing temperature is between 220°C and 240°C.

[0047] Aspect 32: The high melt strength polypropylene of Aspect 30 or 31, wherein the processing temperature is about 230°C. Aspect 33: The high melt strength polypropylene of any of Aspects 30-32, wherein the acid neutralizing agent comprises at least one of a metal oxide, a metal hydroxide, an alkali metal hydroxide, an alkali metal carbonate, an alkaline earth metal oxide, an alkaline earth metal carbonate, an alkali metal bicarbonate, a metal carboxylate, an alkali metal carboxylate, an alkaline earth metal carboxylate, or a combination thereof. Aspect 34: The high melt strength polypropylene of any of Aspects 30-33, wherein the at least one acid neutralizing agent comprises at least one of zinc oxide, zinc hydroxide, calcium oxide, barium oxide, magnesium oxide, titanium dioxide, sodium carbonate, sodium bicarbonate, calcium carbonate, magnesium carbonate, sodium hydroxide, potassium hydroxide, a zinc salt of a fatty acid, a calcium salt of a fatty acid, or a combination thereof. Embodiment 35: The method of any of Embodiments 30-34, wherein the at least one acid neutralizing agent comprises zinc oxide. High melt strength polypropylene. Embodiment 36: The high melt strength polypropylene of any of embodiments 30-35, comprising zinc diacrylate. Aspect 37: The high melt strength polypropylene of any of Aspects 30 to 36, wherein the resin composition does not contain an organic peroxide.

[0041] Aspect 38: The high melt strength polypropylene of any of Aspects 30 to 37, wherein the unfunctionalized polypropylene has a melt flow index (MFI) from 0.2 g / 10 min to 2000 g / 10 min (2.16 Kg, 230°C). Embodiment 39: The high melt strength polypropylene of any of embodiments 30-38, wherein the unfunctionalized polypropylene is at least one of a polypropylene homopolymer, a polypropylene copolymer, or an alloy of polypropylene with at least one additional polymer. Aspect 40: The high melt strength polypropylene of any one of Aspects 30 to 39, wherein the resin composition contains 0.5% by weight to 3% by weight of zinc diacrylate. Aspect 41: The high melt strength polypropylene of any of Aspects 30-40, further comprising at least one of an antioxidant, a filler other than an acid neutralizer, a colorant other than an acid neutralizer, a flame retardant other than an acid neutralizer, a blowing agent other than an acid neutralizer, a clarifier, a scratch prevention additive, a dust prevention additive, a nucleating agent, or a stabilizer. Aspect 42: 0.1 seconds at 170°C -1 42. The high melt strength polypropylene of any of embodiments 30 to 41, having an extensional viscosity measured at a strain rate of at least 1,000,000 Pa·s. Aspect 43: 0.1 seconds at 170°C -1 42. The high melt strength polypropylene of any of embodiments 30 to 41, having an extensional viscosity measured at a strain rate of at least 500,000 Pa·s. Aspect 44: 0.1 seconds at 170°C -1 42. The high melt strength polypropylene of any of embodiments 30-41, having an extensional viscosity measured at a strain rate of at least 25% greater than the extensional viscosity of the unfunctionalized polypropylene. Aspect 45: 0.1 s at 170°C -1 42. The high melt strength polypropylene of any of embodiments 30-41, having an extensional viscosity measured at a strain rate of from 25% to 2000% greater than the extensional viscosity of the unfunctionalized polypropylene. Embodiment 46: The high melt strength polypropylene of any of embodiments 30-45, wherein the compounding is conducted using a single or twin screw extruder, a Banbury mixer, or a roll mill. Aspect 47: The high melt strength polypropylene of any of Aspects 30 to 46, wherein the resin composition is melt extruded. Embodiment 48: The high melt strength polypropylene of any of embodiments 30-47, wherein acrylate moieties from at least one of zinc diacrylate, calcium diacrylate, or aluminum triacrylate are grafted onto unfunctionalized polypropylene to provide acrylate-functionalized polypropylene chains, and the grafted acrylate groups on the acrylate-functionalized polypropylene chains are present in the form of a polyvalent metal or alkaline earth metal salt. Aspect 49: The high melt strength polypropylene of any of Aspects 30 to 48, wherein at least one of zinc diacrylate, calcium diacrylate, or aluminum triacrylate; or the acid neutralizer is in the form of a masterbatch comprising a polyolefin as a carrier resin for the masterbatch. Embodiment 50: A polymeric article comprising, consisting essentially of, or consisting of the high melt strength polypropylene of any of embodiments 30-46. Embodiment 51: The polymeric article of embodiment 50, wherein the polymeric article is a foamed article, a sheet extrusion, a thermoformed article, a blow molded article, a rotational molded article, an extrusion coated article, a cast article, an injection molded article, a pressed article, a fiber, or a film.

[0044] While the embodiments have been described herein in a manner that enables a clear and concise specification to be written, it is intended and will be understood that the embodiments may be combined or separated in various ways without departing from the invention. It will be understood that any preferred features described are applicable to all embodiments described herein.

[0045] In some embodiments, the invention described herein can be construed to exclude any element or method step that does not materially affect the basic and novel characteristics of the invention, and in some embodiments, the invention can be construed to exclude any element or method step not specified herein.

[0046] While preferred embodiments of the present invention have been shown and described herein, it will be understood that such embodiments are provided by way of example only. Numerous variations, modifications, and substitutions will occur to those skilled in the art without departing from the spirit of the invention. It is therefore intended that the appended claims cover all such modifications which are within the spirit and scope of the invention. [Example]

[0047] In all of the examples described below, melt strength was measured as extensional viscosity, which was measured as follows.

[0048] Samples were compression molded from pellets into 2 mm films. The pellets were melted at 210°C for 5 minutes by holding the mold stationary while in contact with both the top and bottom platens. 20,000 pounds (lbs) of pressure was then applied for 2 minutes. The samples were removed and placed in a press at 23°C and 10,000 lbs of pressure to cool. The samples were then removed from the mold and conditioned at 23°C and 50% humidity for 24 hours before measuring the extensional viscosity.

[0049] Sample pieces measuring 4 mm x 12 mm were cut and compression molded into 2 mm films. Each was mounted on a TA Instruments DHR-2 equipped with a SER3 universal testing platform attachment. The samples were subjected to a temperature soak at 170°C for 180 seconds, followed by a 0.1 s saturation at 170°C. -1 An extension rate of 0.05 was applied to give a final strain of 4.0. In the examples below, the peak extensional viscosity measured by this method is reported as the extensional viscosity value. A method and apparatus for measuring extensional viscosity (Sentmanat Extension Rheometer) is also described in U.S. Patent Nos. 6,578,413 and 6,691,569, the contents of both of which are incorporated herein by reference for all purposes.

[0050] (Example 1: Effect of processing temperature on extensional viscosity) 2.8 MFI polypropylene homopolymer (PP) was compounded with zinc diacrylate and zinc oxide in a 20 mm Brabender twin-screw extruder. The sample further contained 0.1 wt% Irganox® 1010 (BASF) as an antioxidant based on the total weight of the composition. The barrel temperature profile of the extruder was controlled to provide a compounding (i.e., processing) melt temperature range between 185°C and 260°C. Sheet specimens of the pelletized material were prepared by compression molding as described above. The elongational viscosity of the sheet specimens was 0.1 s at 170°C as described above. -1 The results unexpectedly showed that the magnitude of the elongational viscosity reached a local maximum at a processing temperature of 230°C, and that the dependence of the elongational viscosity on the processing temperature was not monotonic.

[0051] The maximum values ​​of elongational viscosity at processing temperatures of 200°C, 230°C, and 260°C were 344,000 Pa·s, 1,536,000 Pa·s, and 676,000 Pa·s, respectively. In the case of the control resin composition (not containing zinc diacrylate and zinc oxide), the maximum values ​​of elongational viscosity at processing temperatures of 200°C, 230°C, and 260°C were 344,000 Pa·s, 1,536,000 Pa·s, and 676,000 Pa·s, respectively. The maximum values ​​were 83,000 Pa·s, 67,000 Pa·s, and 41,000 Pa·s, respectively. This data is plotted in Figure 1, which shows that the extensional viscosity reaches a maximum at 230°C, and that the effect of zinc diacrylate is to improve the extensional viscosity compared to samples made without zinc diacrylate. Additionally, differential scanning calorimetry (DSC) was performed on the control (polypropylene without zinc diacrylate / zinc oxide) and the polypropylene with zinc diacrylate and zinc oxide added. Table 1 shows the thermal properties measured by DSC scans.

[0052] [Table 1]

[0053] (Example 2: Effect of adding zinc oxide to polypropylene) Zinc diacrylate and zinc oxide were compounded with 2.8 MFI polypropylene homopolymer as described above using a compounding temperature of 230°C. The sample also contained 0.1 wt% Irganox® 1010 (BASF) as an antioxidant, based on the total weight of the composition. This resulted in a compounded polypropylene with a 35% reduction in free acrylic acid and a 77% increase in extensional viscosity, i.e., 2,719,000 Pa·s, demonstrating that the presence of an acid neutralizer during reactive mixing of polypropylene and acrylate further improves melt strength.

[0054] Example 3: Effect of Zinc Oxide Amount on Elongational Viscosity Compounding and pelletization of the samples was completed on a 20 mm Brabender twin-screw extruder with a length-to-diameter ratio of 40:1. The samples also contained 0.1 wt.% Irganox® 1010 (BASF) as an antioxidant. The screw profile consisted of a feed element with three 60 mm long mixing blocks. These mixing blocks were positioned 150 mm, 320 mm, and 540 mm from the feed throat on the screw, respectively.

[0055] Starting with a cooled feed throat, a flat temperature profile was used as shown in the table below. Barrel temperatures are shown below. The set point that occupied the majority of the temperature zone, i.e., 230°C, was reported as the processing temperature.

[0056] [Table 2]

[0057] The samples produced are shown in the table below. For a 2.8 MFI polypropylene homopolymer, the addition of zinc oxide and zinc diacrylate increased the extensional viscosity during the reaction during extrusion. Increasing the zinc oxide loading further improved the extensional viscosity in combination with zinc diacrylate, as shown in Table 3 below. Note that in Table 2, the amount of zinc oxide is reported as a weight percent based on the total weight of the zinc diacrylate.

[0058] [Table 3]

[0059] As can be seen from the above, the addition of zinc oxide to polypropylene homopolymer containing zinc diacrylate improves melt strength, measured as extensional viscosity.

Claims

1. 1. A high melt strength resin composition comprising: a) a non-functionalized polypropylene; b) at least one of zinc diacrylate, calcium diacrylate, or aluminum triacrylate in a total amount of 0.1% to 5% by weight, based on the weight of the non-functionalized polypropylene; and c) at least one acid neutralizing agent in a total amount of 0.005% to 5% by weight, based on the total weight of the at least one acrylate salt.

2. 2. The high melt strength resin composition of claim 1, wherein the acid neutralizing agent comprises at least one of a metal oxide, a metal hydroxide, an alkali metal hydroxide, an alkali metal carbonate, an alkaline earth metal oxide, an alkaline earth metal carbonate, an alkali metal bicarbonate, a metal carboxylate, an alkali metal carboxylate, an alkaline earth metal carboxylate, and combinations thereof.

3. 2. The high melt strength resin composition of claim 1, wherein the acid neutralizing agent comprises at least one of zinc oxide, zinc hydroxide, calcium oxide, barium oxide, magnesium oxide, titanium dioxide, sodium carbonate, sodium bicarbonate, calcium carbonate, magnesium carbonate, sodium hydroxide, potassium hydroxide, zinc salts of fatty acids, calcium salts of fatty acids, or combinations thereof.

4. 10. The high melt strength resin composition of claim 1, wherein said at least one acid neutralizing agent comprises zinc oxide.

5. The high melt strength resin composition of claim 1 comprising zinc diacrylate.

6. The high melt strength resin composition of claim 1 , wherein the resin composition is free of organic peroxides.

7. 2. The high melt strength resin composition of claim 1, wherein the non-functionalized polypropylene has a melt flow index (MFI) of 0.2 g / 10 min to 2000 g / 10 min (2.16 Kg, 230° C.).

8. 10. The high melt strength resin composition of claim 1, wherein the non-functionalized polypropylene is at least one of a polypropylene homopolymer, a polypropylene copolymer, or an alloy of polypropylene with at least one additional polymer.

9. 10. The high melt strength resin composition of claim 1, wherein the non-functionalized polypropylene is prepared using at least one Ziegler-Natta catalyst.

10. 10. The high melt strength resin composition of claim 1, wherein the unfunctionalized polypropylene is prepared using at least one metallocene catalyst.

11. 10. The high melt strength resin composition of claim 1, wherein the unfunctionalized polypropylene is prepared using free radical initiation.

12. 2. The high melt strength resin composition of claim 1, which contains 0.5% to 3% by weight of an acrylate salt.

13. 10. The high melt strength resin composition of claim 1, further comprising one or more of an antioxidant, a filler other than an acid neutralizer, a colorant other than an acid neutralizer, a flame retardant other than an acid neutralizer, a blowing agent other than an acid neutralizer, a clarifier, a scratch prevention additive, a dust prevention additive, a nucleating agent, or a stabilizer.

14. 1. A method for producing high melt strength polypropylene, the method comprising the steps of compounding a resin composition comprising: a) unfunctionalized polypropylene; b) at least one of zinc diacrylate, calcium diacrylate, and aluminum triacrylate in a total amount of 0.1% to 5% by weight, based on the weight of the unfunctionalized polypropylene; and c) at least one acid neutralizer in a total amount of 0.005% to 5% by weight, based on the total weight of the at least one acrylate salt, at a processing temperature between 185°C and 260°C.

15. 15. The method of claim 14, wherein the processing temperature is between 220°C and 240°C.

16. 15. The method of claim 14, wherein the processing temperature is about 230°C.

17. 15. The method of claim 14, wherein the compounding is carried out using a single or twin screw extruder, a Banbury mixer, or a roll mill.

18. 15. The method of claim 14, wherein at least one of zinc diacrylate, calcium diacrylate, or aluminum triacrylate; or the acid neutralizing agent is in the form of a masterbatch comprising a polyolefin as a carrier resin for the masterbatch.

19. The method of claim 14 wherein the resin composition is melt extruded.

20. 15. The method of claim 14, wherein the compounding results in acrylate moieties from at least one of zinc diacrylate, calcium diacrylate, or aluminum triacrylate being grafted to the non-functionalized polypropylene.

21. 1. A high melt strength polypropylene obtained by compounding, at a processing temperature between 185°C and 260°C, a resin composition comprising: a) a non-functionalized polypropylene; b) at least one acrylate salt of zinc diacrylate, calcium diacrylate, or aluminum triacrylate, in an amount of 0.1% to 5% by weight based on the weight of the non-functionalized polypropylene; and c) at least one acid neutralizer in a total amount of 0.005% to 5% by weight based on the total weight of the at least one acrylate salt.

22. 22. The high melt strength polypropylene of claim 21, wherein the processing temperature is between 220°C and 240°C.

23. 22. The high melt strength polypropylene of claim 21, wherein said processing temperature is about 230°C.

24. 0.1 s at 170°C －１ 22. The high melt strength polypropylene of claim 21, having an extensional viscosity measured at a strain rate of at least 1,000,000 Pa s.

25. 0.1 s at 170°C －１ 22. The high melt strength polypropylene of claim 21, having an extensional viscosity measured at a strain rate of at least 500,000 Pa s.

26. 0.1 s at 170°C －１ 22. The high melt strength polypropylene of claim 21, wherein the extensional viscosity measured at a strain rate of 100 psi is at least 25% higher than the extensional viscosity of unfunctionalized polypropylene.

27. 0.1 s at 170°C －１ 22. The high melt strength polypropylene of claim 21, wherein the extensional viscosity measured at a strain rate of 1000 .mu.m is from 25% to 2000% higher than the extensional viscosity of unfunctionalized polypropylene.

28. 22. The high melt strength polypropylene of claim 21, wherein said compounding is carried out using a single or twin screw extruder, a Banbury mixer, or a roll mill.

29. 22. The high melt strength polypropylene of claim 21, wherein the resin composition is melt extruded.

30. 22. The high melt strength polypropylene of claim 21, wherein acrylate moieties derived from zinc diacrylate, calcium diacrylate, or aluminum triacrylate are grafted to non-functionalized polypropylene to provide acrylate-functionalized polypropylene chains, and the grafted acrylate groups on the acrylate-functionalized polypropylene chains are present in the form of polyvalent metal or alkaline earth metal salts.

31. 22. The high melt strength polypropylene of claim 21 wherein at least one of zinc diacrylate, calcium diacrylate, or aluminum triacrylate; or the acid neutralizing agent is in the form of a masterbatch comprising a polyolefin as a carrier resin for the masterbatch.

32. 22. A polymeric article comprising the high melt strength polypropylene of claim 21.

33. 33. The polymeric article of claim 32, wherein the polymeric article is a foamed article, a sheet extrusion, a thermoformed article, a blow molded article, a rotational molded article, an extrusion coated article, a cast article, an injection molded article, a pressed article, a fiber, or a film.

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